1. Field of the Invention
The present invention relates to an In-Plane Switching mode active matrix liquid crystal display device and a method of manufacturing the same.
2. Related Background Art
Recently, In-Plane Switching mode in which an electric field parallel to a substrate is applied to liquid crystal is employed in an active matrix liquid crystal display device for obtaining an extremely wide viewing angle, as disclosed in Japanese Patent Application Laid-Open No. H08-254712. In-Plane Switching mode operation minimizes viewing-angle-based gray-scale inversion and deterioration in contrast ratio (reference: M. Oh-e et. al., Asia Display 1995. pp. 577–580). FIG. 13A is a plan view showing a pixel area of a conventional In-Plane Switching mode liquid crystal display device, and FIG. 13B is an enlarged sectional view showing a part of the same. In FIGS. 13A and 13B, reference numeral 100 designates a Thin Film Transistor (TFT) array substrate, and 200, a color filter (CF) substrate. Reference numeral 1 designates a gate line that is a plurality of scanning lines formed on an insulating substrate, 2 a gate insulation film, 3 a source line, 4 an insulation film formed on the source line 3, and 5a and 5b common electrodes formed on the same layer as the gate line. As shown in FIG. 13B, the common electrode 5 is separated into the common electrodes 5a and 5b. In this configuration, a voltage applied to the source line generates an electric field E, changing an alignment condition of the liquid crystal placed between the TFT array substrate 100 and the CF substrate 200. Therefore, the width L1 in FIG. 13B has to be wide in the configuration shown in FIGS. 13A and 13B, and light transmission is thus limited, which causes a problem of low aperture ratio.
In order to solve the above problem, a configuration shown in FIGS. 1A and 1B has been proposed. In this configuration, the source line 3 and the common electrode 5 are overlapped with each other, the source line 3 covered with the common electrode 5. Therefore, an electric field generated from the source line 3 is blocked by the common electrode 5 not to reach the liquid crystal, thereby reducing change in an alignment condition of the liquid crystal. Accordingly, the width L2 to limit light transmission can be small, thus attaining high aperture ratio.